This invention relates to an improved solar collector system.
In another aspect, this invention relates to a solar collector system wherein the reflective surfaces of the system are supported by an improved support structure. In still another aspect, this invention relates to a solar collector system wherein the reflective surfaces are disposed on a support structure having improved structural properties. In yet another aspect, this invention relates to a solar collector system wherein the entire system is constructed to withstand varying wind loads without decreasing the efficiency of the system.
Recent economic and political developments have resulted in a dramatic increase in the cost of energy sources such as conventional crude oil, natural gas and the like. Because of the increased prices of crude oil, natural gas and the like, and as a result of very real and potential shortages of such conventional energy sources, alternative sources of energy are being investigated. It has long been known that solar radiation or "solar energy" is a vast, untapped source of energy. Unfortunately, work done in the area of recovering energy from the sun has not been widespread due to economic reasons. Now, it is very apparent that the availability and price of conventional energy sources will make alternative energy sources economically competitive.
Much of the most recent investigations dealing with the recovery of solar energy has centered around studies of various solar collectors. Such solar collectors include tubes, mats, and other large surface area solar collectors that contain some type of working fluid that is heated by merely placing such large solar collectors in the sun. Such solar collectors are effective in heating the working fluids only a few degrees above the ambient temperature. Additionally, such large solar collectors are relatively expensive.
There are many types of solar collectors being designed and studied to gather solar energy and concentrate the solar energy into a relatively small area to thereby achieve high temperatures. Such solar collectors usually involve some type of lens or prism reflective means or some type of a reflective surface means that will concentrate solar radiation that is radiated onto a relatively large reflective surface area onto a relatively small target or energy collector means. It has been found that the use of highly reflective surfaces or mirror type surfaces are very effective for gathering solar radiation striking a relatively large effective area and focusing or concentrating the radiation onto a relatively small target area or energy receiver. Such types of solar collectors include a collection of many individual, flat mirrors that can be focused onto one small target or energy collector, as well as various types of curved and shaped reflective surfaces that will focus the thus collected solar energy onto a relatively small surface or energy receiver.
As the art of collecting solar energy has evolved, it has been found that the use of solar collectors that can be aimed directly at the sun to collect a maximum amount of solar radiation and thereby concentrate or focus the radiation by reflecting it onto a relatively small target or energy receiver are most desirable. Parabolic reflectors have been widely studied. However, as a result of the high cost of construction, as well as the technical problems in constructing such parabolic reflectors, such parabolic reflectors are not widely used for low cost energy recovery from the sun.
Recently, "trough-like" reflectors have been investigated as relatively low cost types of solar collectors. The trough-like reflectors have proven to be much less expensive to manufacture than true parabolic reflectors. Some of the most effective trough-like reflectors utilize a relatively large reflector surface that is formed by constructing an elongated trough-like means with the walls of the trough having a constant parabolic shape whereby the focal point of the parabolic trough lies along a relatively straight line above the parabolic trough. Thus, the concave trough-like solar collector can be equipped with a target or energy receiver that is disposed along the line formed by the focal point of the parabolic reflector. The most effective types of trough-like reflectors further include means for aiming or pointing the parabolic reflector toward the sun whereby the axis of the parabola is pointed as nearly as possible directly toward the sun. Suitable control and tracking mechanisms are known in the art whereby the axis of the parabola can substantially track the sun as the sun traverses the sky.
While the above-mentioned trough-like solar collectors are widely used in solar energy recovery systems, many problems still exist. Probably, one of the most serious problems connected with such trough-like reflectors is the formation of reflectorized surfaces that have substantially parabolic properties to insure proper focusing or targeting of the reflected solar energy on an energy receiver. Much work has been done on perfecting techniques for insuring a good paragolic surface area for such reflectors.
Probably, the most widespread method for forming such trough-like reflectors is to utilize a "torque tube" which is essentially a large diameter pipe, rod, or tube. Conventional methods for forming such trough-like reflectors utilize the torque tube as the central load bearing member and various ribs, beams, braces and the like are rigidly affixed to the torque tube. Once the ribs, beams or braces are rigidly affixed to the torque tube, the reflectorized surface of the solar collector is affixed to the upper surfaces of the ribs, beams or braces. One widespread method for forming the reflectorized surface is to bend and shape sheet metal to a desired configuration and thereafter rigidly affix the sheet metal to the ribs or beams which are, in turn, carried by the torque tube. Thereafter, the metal can either be polished or some type of reflective medium can be applied to the base to provide the reflective surface.
Since it is imperative that solar collectors be located out of doors to attain maximum energy recovery, it is apparent that a very real and serious problem is presented when large solar collectors are exposed to wind loads. Since the reflector surfaces are rather large in most cases, winds of even a moderate velocity will cause conventionally constructed solar collectors to bend and twist and even sometimes fail altogether as a result of the wind forces. The solution to the problem has been to add structural members that will stiffen and further brace the surfaces of the solar collector. As a result of such methods for increasing the structural integrity of solar collectors, most solar collectors are extremely heavy and cumbersome. This, of course, creates a problem when the solar collector must be placed on rooftops and the like. Additionally, the conventional types of solar collectors are all carried by the above-mentioned "torque tube" which must be designed to withstand tremendous torque stresses. However, no effective construction technique has been suggested for minimizing the weight of solar collectors that must be designed to withstand high wind loads.
It is, thus, very apparent that there is a need for improved solar collector systems. It is also evident that there is a tremendous need for solar collector systems that can be constructed of readily available materials and have light weight, but be of such construction as to withstand the ravages of high wind loads.